A large and growing population of people is enjoying entertainment through consumption of digital content items, such as music, movies, images, books and so on. Many people today consume digital content through a wide variety of electronic devices. Among these electronic devices are cellular telephones, personal digital assistants (PDAs), electronic book readers, portable media players, tablets, netbooks and the like. Devices such as this traditionally rely on input mechanisms such as keyboards, which require physical manipulation by a user. Increasingly, however, it is desired to detect and monitor the physical positions and movements of users and objects within an environment, and to respond to gestures and other actions of a user without dedicated physical input devices.